/**
 *create by 2014年7月9日 http://javascript.css-js.com/
 *BASE64 Encode and Decode By UTF-8 unicode
 *可以和java的BASE64编码和解码互相转化
 */
var BASE64_MAPPING = [
    'A','B','C','D','E','F','G','H',
    'I','J','K','L','M','N','O','P',
    'Q','R','S','T','U','V','W','X',
    'Y','Z','a','b','c','d','e','f',
    'g','h','i','j','k','l','m','n',
    'o','p','q','r','s','t','u','v',
    'w','x','y','z','0','1','2','3',
    '4','5','6','7','8','9','+','/'
];
/**
 *ascii convert to binary
 */
var _toBinary = function(ascii){
    var binary = new Array();
    while(ascii > 0){
        var b = ascii%2;
        ascii = Math.floor(ascii/2);
        binary.push(b);
    }
    /*
    var len = binary.length;
    if(6-len > 0){
      for(var i = 6-len ; i > 0 ; --i){
        binary.push(0);
      }
    }*/
    binary.reverse();
    return binary;
};
/**
 *binary convert to decimal
 */
var _toDecimal = function(binary){
    var dec = 0;
    var p = 0;
    for(var i = binary.length-1 ; i >= 0 ; --i){
        var b = binary[i];
        if(b == 1){
            dec += Math.pow(2 , p);
        }
        ++p;
    }
    return dec;
};
/**
 *unicode convert to utf-8
 */
var _toUTF8Binary = function(c , binaryArray){
    var mustLen = (8-(c+1)) + ((c-1)*6);
    var fatLen = binaryArray.length;
    var diff = mustLen - fatLen;
    while(--diff >= 0){
        binaryArray.unshift(0);
    }
    var binary = [];
    var _c = c;
    while(--_c >= 0){
        binary.push(1);
    }
    binary.push(0);
    var i = 0 , len = 8 - (c+1);
    for(; i < len ; ++i){
        binary.push(binaryArray[i]);
    }
    for(var j = 0 ; j < c-1 ; ++j){
        binary.push(1);
        binary.push(0);
        var sum = 6;
        while(--sum >= 0){
            binary.push(binaryArray[i++]);
        }
    }
    return binary;
};
var BASE64 = {
    /**
     *BASE64 Encode
     */
    encoder:function(str){
        var base64_Index = [];
        var binaryArray = [];
        for(var i = 0 , len = str.length ; i < len ; ++i){
            var unicode = str.charCodeAt(i);
            var _tmpBinary = _toBinary(unicode);
            if(unicode < 0x80){
                var _tmpdiff = 8 - _tmpBinary.length;
                while(--_tmpdiff >= 0){
                    _tmpBinary.unshift(0);
                }
                binaryArray = binaryArray.concat(_tmpBinary);
            }else if(unicode >= 0x80 && unicode <= 0x7FF){
                binaryArray = binaryArray.concat(_toUTF8Binary(2 , _tmpBinary));
            }else if(unicode >= 0x800 && unicode <= 0xFFFF){//UTF-8 3byte
                binaryArray = binaryArray.concat(_toUTF8Binary(3 , _tmpBinary));
            }else if(unicode >= 0x10000 && unicode <= 0x1FFFFF){//UTF-8 4byte
                binaryArray = binaryArray.concat(_toUTF8Binary(4 , _tmpBinary));
            }else if(unicode >= 0x200000 && unicode <= 0x3FFFFFF){//UTF-8 5byte
                binaryArray = binaryArray.concat(_toUTF8Binary(5 , _tmpBinary));
            }else if(unicode >= 4000000 && unicode <= 0x7FFFFFFF){//UTF-8 6byte
                binaryArray = binaryArray.concat(_toUTF8Binary(6 , _tmpBinary));
            }
        }
        var extra_Zero_Count = 0;
        for(var i = 0 , len = binaryArray.length ; i < len ; i+=6){
            var diff = (i+6)-len;
            if(diff == 2){
                extra_Zero_Count = 2;
            }else if(diff == 4){
                extra_Zero_Count = 4;
            }
            //if(extra_Zero_Count > 0){
            // len += extra_Zero_Count+1;
            //}
            var _tmpExtra_Zero_Count = extra_Zero_Count;
            while(--_tmpExtra_Zero_Count >= 0){
                binaryArray.push(0);
            }
            base64_Index.push(_toDecimal(binaryArray.slice(i , i+6)));
        }
        var base64 = '';
        for(var i = 0 , len = base64_Index.length ; i < len ; ++i){
            base64 += BASE64_MAPPING[base64_Index[i]];
        }
        for(var i = 0 , len = extra_Zero_Count/2 ; i < len ; ++i){
            base64 += '=';
        }
        return base64;
    },
    /**
     *BASE64 Decode for UTF-8
     */
    decoder : function(_base64Str){
        var _len = _base64Str.length;
        var extra_Zero_Count = 0;
        /**
         *计算在进行BASE64编码的时候，补了几个0
         */
        if(_base64Str.charAt(_len-1) == '='){
            //alert(_base64Str.charAt(_len-1));
            //alert(_base64Str.charAt(_len-2));
            if(_base64Str.charAt(_len-2) == '='){//两个等号说明补了4个0
                extra_Zero_Count = 4;
                _base64Str = _base64Str.substring(0 , _len-2);
            }else{//一个等号说明补了2个0
                extra_Zero_Count = 2;
                _base64Str = _base64Str.substring(0 , _len - 1);
            }
        }
        var binaryArray = [];
        for(var i = 0 , len = _base64Str.length; i < len ; ++i){
            var c = _base64Str.charAt(i);
            for(var j = 0 , size = BASE64_MAPPING.length ; j < size ; ++j){
                if(c == BASE64_MAPPING[j]){
                    var _tmp = _toBinary(j);
                    /*不足6位的补0*/
                    var _tmpLen = _tmp.length;
                    if(6-_tmpLen > 0){
                        for(var k = 6-_tmpLen ; k > 0 ; --k){
                            _tmp.unshift(0);
                        }
                    }
                    binaryArray = binaryArray.concat(_tmp);
                    break;
                }
            }
        }
        if(extra_Zero_Count > 0){
            binaryArray = binaryArray.slice(0 , binaryArray.length - extra_Zero_Count);
        }
        var unicode = [];
        var unicodeBinary = [];
        for(var i = 0 , len = binaryArray.length ; i < len ; ){
            if(binaryArray[i] == 0){
                unicode=unicode.concat(_toDecimal(binaryArray.slice(i,i+8)));
                i += 8;
            }else{
                var sum = 0;
                while(i < len){
                    if(binaryArray[i] == 1){
                        ++sum;
                    }else{
                        break;
                    }
                    ++i;
                }
                unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+1 , i+8-sum));
                i += 8 - sum;
                while(sum > 1){
                    unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+2 , i+8));
                    i += 8;
                    --sum;
                }
                unicode = unicode.concat(_toDecimal(unicodeBinary));
                unicodeBinary = [];
            }
        }
        //---------直接转换为结果
        var strResult = '';
        for(var i = 0 , len = unicode.length ; i < len ;++i){
            strResult += String.fromCharCode(unicode[i]);
        }
        return strResult;
    }
};

